The Safety of Bilateral Simultaneous Hip and Knee Arthroplasty versus Staged Arthroplasty in a High-Volume Center Comparing Blood Loss, Peri- and Postoperative Complications, and Early Functional Outcome.

PURPOSE: In recent years, there has been increasing interest in the use of simultaneous hip and knee arthroplasty compared to staged procedures in patients with bilateral pathology. The aim of this study was to compare simultaneous and staged hip and knee arthroplasty in patients with bilateral pathology by assessing the transfusion rate, postoperative hemoglobin drop, length of stay (LOS), in-hospital complications, 30-day readmissions and early functional outcome. METHODS: We conducted a retrospective cohort study that included all patients who were undergoing primary TKA, THA and UKA by a single surgeon in a high-volume arthroplasty center between 2015 and 2020 as simultaneous or staged procedures. Staged bilateral arthroplasties were performed within 12 months and were stratified by the time between procedures. Data were acquired through the electronic files at the Orthopädische Chirurgie München (OCM). For functional outcome, the ability of the patients to walk independently on the ward was compared with the ability to walk a set of stairs alone, which was recorded daily by the attending physiotherapist. RESULTS: In total n = 305 patients were assessed for eligibility and included in this study. One hundred and forty-five patients were allocated to the staged arthroplasty group. This group was subdivided into a hip and a knee group, whereas the knee group was split into TKA and UKA. The second staged procedure was performed within 12 months of the first procedure. One hundred and sixty patients were allocated to the simultaneous arthroplasty group. This group was also subdivided into a hip and knee group, whereas the knee group was split again into a TKA and UKA group. No statistical difference was found between the two groups regarding demographic data. Primary outcome measurements: There was no significant difference in the transfusion rate or complication rate. Secondarily, no statistically significant difference was found between the postoperative hemoglobin drop and the functional outcome, or in the length of stay (LOS) between both groups. Walking the stairs showed a significant difference in the knee group. CONCLUSIONS: There were no significant differences observed in the transfusion rate in-hospital complications, or readmission rate between both groups. The early functional outcome showed no significant difference in mobility for all groups. Simultaneous arthroplasty for knee or hip is as safe as a staged procedure, with no higher risk for the patient, in a specialized high-volume center. LEVEL OF EVIDENCE: Level IV.

Efficacy of antibiotic treatment of implant-associated Staphylococcus aureus infections with moxifloxacin, flucloxacillin, rifampin, and combination therapy: an animal study.

The efficacy of antibiotic monotherapy and combination therapy in the treatment of implant-associated infection by Staphylococcus aureus was evaluated in an animal study. The femoral medullary cavity of 66 male Wistar rats was contaminated with S. aureus (ATCC 29213) and a metal device was implanted, of which 61 could be evaluated. Six treatment groups were studied: flucloxacillin, flucloxacillin in combination with rifampin, moxifloxacin, moxifloxacin in combination with rifampin, rifampin, and a control group with aqua. The treatment was applied for 14 days. After euthanasia, the bacterial counts in the periprosthetic bone, the soft tissue, and the implant-associated biofilm were measured. Both antibiotic combination treatments (moxifloxacin plus rifampin and flucloxacillin plus rifampin) achieved a highly significant decrease in microbial counts in the bone and soft tissue and in the biofilm. Mono-antibiotic treatments with either moxifloxacin or flucloxacillin were unable to achieve a significant decrease in microbial counts in bone and soft tissue or the biofilm, whilst rifampin was able to reduce the counts significantly only in the biofilm. Antibiotic resistance was measured in 1/3 of the cases in the rifampin group, whereas no resistance was measured in all other groups. The results show that combinations of both moxifloxacin and flucloxacillin plus rifampin are adequate for the treatment of periprosthetic infections due to infections with S. aureus, whereas monotherapies are not effective or not applicable due to the rapid development of antibiotic resistance. Therefore, moxifloxacin is an effective alternative in combination with rifampin for the treatment of implant-associated infections.

Validation of a measurement device for instrumented quantification of anterior translation and rotational assessment of the knee.

PURPOSE: A test setup for clinical use in the awake and non-anesthetized patient measuring anteroposterior translation and rotation of the knee joint is the subject of validation. METHODS: A measuring device featuring fixation of the foot at 30° of knee flexion with varus/valgus stress posts for the knee was developed. Tibial rotation (external/internal) was imposed with a torque of 2 Nm on the footrest with the ankle locked in dorsiflexion. Anterior translation of the tibia in relation to the femur was measured with a commercially available arthrometer. Measurements were performed in a neutral position, internal rotation, and external rotation. Intrarater and inter-rater reliability was validated in 10 healthy volunteers (Cronbach α). We examined 10 patients with isolated anterior cruciate ligament (ACL) rupture, as well as 10 patients with ACL rupture plus medial instability and 10 patients with additional lateral instability. Side-to-side differences were used for calculation. RESULTS: Comparison of healthy volunteers and subjects with isolated ACL rupture showed significant differences: internal rotation, 0.79 mm and 2.46 mm, respectively (P = .001); neutral position, 0.4 mm and 3.35 mm, respectively (P < .0001); and external rotation, 0.29 mm and 2.5 mm, respectively (P = .003). Significant differences (P = .008) were found between isolated ACL rupture and ACL rupture plus medial instability by use of the ratio of anterior translation in external rotation versus the neutral position. Inter-rater reliability was 0.948 in 10 healthy volunteers and 0.981 in 10 subjects with unilateral ACL rupture. Intrarater reliability in the volunteers was 0.829. CONCLUSIONS: By use of the developed measurement device, the "Laxitester" (ORTEMA Sport Protection, Markgroeningen, Germany), objective differentiation between isolated ACL rupture and ACL rupture plus additional medial instability is possible. Values for anterior translation are reliable and reproducible by different examiners and by the same examiner at different times. CLINICAL RELEVANCE: The Laxitester allows objectification of medial instability in combination with ACL injuries and provides a reference regarding the need for additional medial stabilization. Compared with the isolated measurement of anteroposterior translation, knee instability can be assessed in a more differentiated manner.

Accuracy of acetabular cup placement in computer-assisted, minimally-invasive THR in a lateral decubitus position.

In a prospective and randomised clinical study, we implanted acetabular cups either by means of an image-free computer-navigation system (navigated group, n = 32) or by free-hand technique (freehand group n = 32, two drop-outs). Total hip replacement was conducted in the lateral position and through a minimally invasive anterior approach (MicroHip). The position of the component was determined postoperatively on CT scans of the pelvis using CT-planning software. We found an average inclination of 42.3° (range 32.7-50.6°; SD ± 3.8°) and an average anteversion of 24.5° (range 12.0-33.3°; SD ± 6.0°) in the computer-assisted study group and an average inclination of 37.9° (range 25.6-50.2°; SD ± 6.3°) and an average anteversion of 23.8° (range 5.6-46.9°; SD ± 10.1°) in the freehand group. The higher precision of computer navigation was indicated by the lower standard deviations. For both measurements we found a significant heterogeneity of variances (p < 0.05, Levene's test). The mean difference between the cup inclination/anteversion values displayed by computer navigation and the true cup position (CT control) was 0.37° (SD 3.26) and -5.61° (SD 6.48), respectively. We found a bias (underestimation) with regard to anteversion determined by the imageless computer navigation system. A bias for inclination was not found. Registration of the landmarks of the anterior pelvic plane in lateral position with undraped percutaneous methods leads to an error in cup anteversion, but not to an error in cup inclination. The bias we found is consistent with a correct registration of the anterosuperior iliac spine (ASIS) and with a registration of the symphysis 1 cm above the bone, corresponding to the less compressible overlying soft tissue in this region. There was no significant correlation between the bias and the thickness of soft tissue above the pubic tubercles. We suggest use of a percutaneous registration of ASIS and an invasive registration above the pubic tubercles when computer-assisted navigation is performed in minimally invasive THR in a lateral position.

Experimental validation of a pinless femoral reference array for computer-assisted hip arthroplasty.

The use of computer navigation systems during total hip arthroplasty requires the femoral fixation of a reflective dynamic reference base (DRB), which theoretically involves the risk of bony fracture, infection, and pin loosening. The first objective of this study was to evaluate the relative movements between a novel, noninvasive external femoral DRB system and the femur. Secondly, the maximum effects of these 3D movements on intraoperative, computer-assisted leg length and offset measures were evaluated. An imageless navigation system was used to track the positions of the soft tissue attached, pinless DRB relative to an invasive reference marker on the femur during a less-invasive, anterior surgical hip approach. Relative translatory movements up to 8.2 mm mediolaterally and up to 8.8 degrees in rotation were measured. Using a measurement technique in which the calculation of leg length and offset changes is primarily based on a specific realignment of the leg, maximum differences of 1.3 mm for leg length and 1.2 mm for offset were found when comparing the pin-based and pinless methods. Thus, invasive fixation techniques with screws or pins are still the method of choice when standard measurement algorithms for intraoperative leg length and offset measures are used. Though direct translatory and rotational variations between the pinless array and the femoral bone were detected, the pinless array can be used to assess leg length and offset when used with a specific measurement technique that compensates for such variations.

Leg length and offset measures with a pinless femoral reference array during THA.

The bony fixation of reference marker arrays used for computer-assisted navigation during total hip arthroplasty (THA) theoretically involves the risk of fracture, infection, and/or pin loosening. We asked whether intraoperative assessment of leg length (LL) and offset (OS) changes would be accurate using a novel pinless femoral reference system in conjunction with an imageless measurement algorithm based on specific realignment of the relationship between a dynamic femoral and pelvis reference array. LL/OS measurements were recorded during THA in 17 cadaver specimen hips. Preoperatively and postoperatively, specimens were scanned using CT. Linear radiographic LL/OS changes were determined by two investigators using visible fiducial landmarks and image processing software. We found a high correlation of repeated measurements within and between (both 0.95 or greater) the two examiners who did the CT assessments. Pinless LL/OS values showed mean differences less than 1 mm and correlations when compared with CT measurements.

Computer-assisted total hip arthroplasty: coding the next generation of navigation systems for orthopedic surgery.

This article outlines the scientific basis and a state-of-the-art application of computer-assisted orthopedic surgery in total hip arthroplasty (THA) and provides a future perspective on this technology. Computer-assisted orthopedic surgery in primary THA has the potential to couple 3D simulations with real-time evaluations of surgical performance, which has brought these developments from the research laboratory all the way to clinical use. Nonimage- or imageless-based navigation systems without the need for additional pre- or intra-operative image acquisition have stood the test to significantly reduce the variability in positioning the acetabular component and have shown precise measurement of leg length and offset changes during THA. More recently, computer-assisted orthopedic surgery systems have opened a new frontier for accurate surgical practice in minimally invasive, tissue-preserving THA. The future generation of imageless navigation systems will switch from simple measurement tasks to real navigation tools. These software algorithms will consider the cup and stem as components of a coupled biomechanical system, navigating the orthopedic surgeon to find an optimized complementary component orientation rather than target values intraoperatively, and are expected to have a high impact on clinical practice and postoperative functionality in modern THA.

Measuring leg length and offset with an imageless navigation system during total hip arthroplasty: is it really accurate?

BACKGROUND: A novel imageless measurement algorithm to assess leg length (LL) and offset (OS) changes during total hip arthroplasty (THA) has been established, the purpose of this study was to describe the process and establish whether or not it is accurate. METHODS: THA was performed on 17 cadaver hip specimens. LL and OS changes were determined intra-operatively, using an imageless navigation system. Pre- and postoperatively, all specimens had a computed tomography scan (CT) and the LL and OS changes were analysed by two blinded investigators. RESULTS: With mean differences of less than 1 mm (LL, 0.74; SD, 2.4 mm; OS, 0.89; SD, 1.8 mm) supported by substantial significant correlations [r = 0.83 (LL) and r = 0.92 (OS)] imageless navigation values demonstrated a high accuracy when compared to CT measurements. CONCLUSIONS: Intra-operative LL and OS measures are reliable and accurate when using an imageless calculation algorithm which stores the position of the femoral reference frame in relation to the pelvic coordinate system before and after reconstruction.

In vitro investigation of the influence of pelvic tilt on acetabular cup alignment.

This study investigates the influence of pelvic tilt on conventional alignment of acetabular cups. Cementless cups were aligned into a synthetic replica of the pelvis 300 times at different pelvic tilts. At +10 degrees pelvic tilt, average cup inclination was 46.2 degrees (32 degrees to 65 degrees ; +/-7.0 degrees ), and average cup anteversion was 19.8 degrees (4 degrees to 37 degrees ; +/-9.1 degrees ). At neutral pelvic tilt, inclination was 44.5 degrees (28 degrees to 59 degrees ; +/-7.2 degrees ), and anteversion was 15.6 degrees (-5 degrees to 33 degrees ; +/-8.1 degrees ). At -10 degrees pelvic tilt, inclination was 42.6 degrees (25 degrees to 61 degrees ; +/-7.2 degrees ), and anteversion was 10.5 degrees (-10 degrees to 37 degrees ; +/-12.2 degrees ). Overall, 50% of the cups were positioned outside the safe zone: 46% in pelvic inclination, 42% in neutral position, and 63% in pelvic reclination (P = .007). This study shows the considerable inaccuracies of conventional cup implantation by experienced and trainee surgeons and shows the influence of pelvic tilt on acetabular cup alignment.

Accuracy of imageless stem navigation during simulated total hip arthroplasty.

BACKGROUND AND PURPOSE: New computer-assisted measurement algorithms have been established to support the surgeon during total joint replacement intraoperatively. We asked whether the assessment of leg length and offset measured with an imageless navigation system is reliable during simulated total hip arthroplasty in a sawbone model test bench. METHODS AND RESULTS: We found no statistically significant difference between change in leg length and offset measured on a millimeter scale connected to the test bench and that obtained with the calculation algorithm of the imageless navigation system. INTERPRETATION: Measurement of leg length and offset with an imageless navigation system is reliable during simulated total hip arthroplasty. The leg length situation algorithm offers the advantage of measuring leg length and offset by determination of the change in position of the femur relative to the pelvic coordinate system without the need to calculate the center of rotation of the hip joint. Further studies should address the accuracy of this imageless stem navigation method in an anatomical and clinical setting.

An experimental comparison of different devices for pulsatile high-pressure lavage and their relevance to cement intrusion into cancellous bone.

INTRODUCTION: Some of the systems marketed for pulsatile high-pressure lavage are clearly different in their mechanical pulse characteristics. To take the matter further we set up an experimental in vitro model to determine whether these different lavage systems might produce different cementation results because of their differing pulse characteristics, and whether the systems differed significantly in terms of cement depth penetration. MATERIALS AND METHODS: A total of 48 femoral heads were obtained at operation from patients who had undergone endoprosthetic hip replacement. The specimens were subjected to manual rinsing or semiautomatic cleansing procedures with five different pulsatile lavage devices. After the cleansing procedures, polymethylmetacrylate bone cement was intruded into the cancellous bone under standardised conditions. Determination of cement penetration was done by computed tomography using an image processing software. RESULTS: Irrespective of the nature of the lavage system tested, superficial cement penetration, both up to 2 mm and up to 3 mm, was significantly better after pulsatile high-pressure lavage than it was after manual rinsing of the specimens with a bladder syringe (P < 0.001 in each case). Whereas our experimental model did not show any significant differences between the lavage systems as regards the cementation results to a depth of up to 2 mm (P = 0.996), there were significant differences at a target depth of 3 mm (P < 0.05). CONCLUSION: As compared with manual rinsing, pulsatile high-pressure lavage in vitro makes highly significant improvements in cement penetration into cancellous bone and should be regarded as an indispensable component of modern cementation techniques for endoprosthetic surgery. Up to the present we have not been able to ascertain what influence the different pulse characteristics of a pulsatile lavage system may have on the intended cementation result, whether it is impact force, pulse shape, pulse duration, flow rate or frequency. Appropriate investigations will be necessary.

Tissue concentrations of vancomycin and Moxifloxacin in periprosthetic infection in rats.

BACKGROUND: A one-step exchange of an endoprosthesis with periprosthetic infection requires effective antibiotics at high concentrations around the endoprosthesis. We evaluated the tissue distribution of vancomycin and Moxifloxacin in a standardized in vivo model of periprosthetic infection. METHODS: 36 male rats with periprosthetic infection of the left hind leg, induced by a standardized procedure, received either antibiotic treatment with vancomycin or Moxifloxacin twice daily for 2 weeks, or a sham treatment. After the last administration, different tissues from each animal were evaluated for concentrations of antibiotic. RESULTS: Compared to plasma, the tissue concentrations of Moxifloxacin were higher in all tissues investigated (lung, muscle, fat, bone) and the tissue-plasma ratio of Moxifloxacin was considerably higher than that of vancomycin. The concentrations of Moxifloxacin were equally high in the infected and the uninfected hind leg, whereas the vancomycin concentrations were significantly higher in the infected leg. INTERPRETATION: The standardized model of periprosthetic infection described here can be extrapolated to different bacterial and mycotic pathogens, and also to different antibiotics or therapeutic regimes. It provides a way of correlating tissue concentrations with clinical outcome in future studies.

Moxifloxacin superior to vancomycin for treatment of bone infections--a study in rats.

BACKGROUND: Increasing resistance rates towards conventional antibiotics necessitate investigations of the efficacy of newly developed antibiotics. Thus, in a rat study, we compared the efficacy of moxifloxacin and vancomycin in the treatment of a local Staphylococcus aureus bone infection. METHOD: The femoral medullary cavities of 36 Wistar rats were contaminated with 100 muL of an oxacillin-sensitive Staphylococcus aureus strain (ATCC 29213) at 10(8) cfu/mL. On the seventh day, antibiotic treatment with moxifloxacin (10 mg/kg twice daily i.p.) or vancomycin (15 mg/kg twice daily i.p.) was commenced in 12 animals each. 12 control animals were left untreated. After 21 days, the infected femurs were explanted and the bacterial counts (cfu/g) were determined. RESULTS: In the control group, a median of 3.42 x 10(6) cfu/g (LQ/UQ 1.09 x 10(6)/ 1.55 x 10(7)) was cultured, with a median of 2.53 x 10(6) cfu/g (LQ/UQ 1.95 x 10(6)/ 4.25 x 10(6)) in the vancomycin group and a median of 2.49 x 10(5) cfu/g (LQ/UQ 2.84 x 10(4)/ 3.75 x 10(5)) in the moxifloxacin group. The bacterial count was reduced by treatment with moxifloxacin both in comparison with the control group (p < 0.001), and in comparison with treatment with vancomycin (p < 0.001). There was no statistically significant difference between the vancomycin group and the control group (p = 0.53). INTERPRETATION: In contrast to vancomycin, moxifloxacin proved to be an effective antibiotic for the treatment of bone infections due to Staphylococcus aureus in our animal model.

Treatment of implant-associated infections with moxifloxacin: an animal study.

The efficacy of moxifloxacin in the treatment of an implant-associated infection by Staphylococcus aureus was compared with vancomycin in an animal study. The femoral medullary cavity of 36 Wistar rats was contaminated with S. aureus (ATCC 29213) and a metal device was implanted. After treatment for 14 days with moxifloxacin (2 x 10 mg/kg/day) or vancomycin (2 x 15 mg/kg/day), the bacterial counts (colony-forming units) in the periprosthetic bone, the soft tissue and the implant-associated biofilm were measured. Compared with the control group, moxifloxacin achieved a highly significant decrease in the microbial counts in the bone and soft tissue and in the biofilm (P<0.001). Moreover, the efficacy of moxifloxacin was significantly greater than that of vancomycin (P<0.01). Vancomycin did not reduce the microbial count significantly compared with the control group (P>0.05). The results justify further investigations of the treatment of implant-associated infections due to S. aureus with moxifloxacin.

Position of the acetabular cup -- accuracy of radiographic calculation compared to CT-based measurement.

OBJECTIVE: A variety of mathematical and trigonometric methods has been described for determining the position of the acetabular cups from conventional radiographs. However, these formulae are subject to unduly large inaccuracies. The aim of the study was to compare the reliability and the accuracy of radiological and CT-based determination of acetabular cup position. MATERIALS AND METHODS: The positions of acetabular cups of 31 patients were calculated in conventional plain radiographs of the hip using the method described by Widmer. Further, in all patients computed tomograms of the pelvis were performed and the cup position was measured with the aid of a CT-based computer-assisted navigation software. As reference values inclination and anteversion of the cups were calculated in 3D reconstructions of the pelvis with the aid of an image processing software. RESULTS: The radiological measurement as well as the CT-based method showed good intra- and inter-observer reliability and no significant difference in the calculation of the inclination (p=0.409). However, CT-based determination of anteversion was significantly more exact than radiological measurement (p<0.001). The calculation of the cup anteversion from the X-rays showed serious deviations from the reference method and a substantial error range (X-ray: mean deviation +1.74 degrees, range -16.6 degrees to +29.8 degrees , S.D. +/-9.32 degrees; CT-based: mean deviation -0.74 degrees, range -6.6 degrees to +5.3 degrees, S.D. +/-2.87). CONCLUSION: For any clinical problem or for clinical studies in which acetabular positions of acetabular cups have to be exactly determined, CT-based measuring methods are obviously the method of choice. Evaluations based only on conventional plain X-rays and calculation of the acetabular cup position using the formula described by Widmer must be regarded as unreliable, particularly, because of problems in measuring the anteversion.

Contaminant seeding in bone by different irrigation methods: an experimental study.

OBJECTIVE: This study was designed to investigate the effectiveness of using various devices and manual procedures for cleansing bacterially contaminated bone tissue and to assess the risk of iatrogenic bacterial seeding in deep bone layers. METHODS: In an in vitro model, human femoral heads were contaminated with Escherichia coli and then cleansed with pulsatile high-pressure lavage, pulsatile low-pressure lavage, manual rinsing with bulb syringe lavage, or manual rinsing with combined brush cleaning. The numbers of bacteria that remained or those that were introduced by the rinsing procedures were quantitatively determined at depths of 0 to 1 cm, 1 to 2 cm, and 2 to 3 cm. RESULTS: Both pulsatile high-pressure lavage and brush cleaning were more effective than pulsatile low-pressure lavage and bulb syringe lavage for the purpose of surface cleansing. The differences were highly significant (P < 0.001). There was no significant difference in the decontaminating effect between pulsatile high-pressure lavage and brush cleaning (P = 0.24). The bacterial contamination attributable to the cleansing procedure, as measured at tissue depths of 1 to 2 cm and 2 to 3 cm, was significantly higher after pulsatile high-pressure lavage and after pulsatile low-pressure lavage than it was after bulb syringe lavage or brush cleaning (P < 0.001). CONCLUSION: In this in vitro investigation of cancellous bone, the brush cleansing was just as effective for getting rid of bacterial contamination as pulsatile high-pressure lavage, and carries a significantly lesser risk of iatrogenic bacterial seeding into deeper tissue layers. In the light of these promising results obtained by the cleansing of cancellous bone contaminated with bacteria, it would be desirable to perform supplementary in vitro and in vivo investigations into brush cleansing.

Arthroscopic and histologic findings in Morquio's syndrome.

Mucopolysaccharidosis type IV A/B (Morquio's syndrome) is one of a heterogeneous group of lysosomal storage diseases characterized by accumulation of keratan sulfate in cells of connective tissue. From early childhood, the major orthopaedic manifestations are shortening of the trunk, spondylepiphyseal dysplasia, odontoid hypoplasia, upper cervical instability, lower-limb alignment problems, and degenerative joint disease. Most of the rare published case reports describe those characteristic clinical deformities of the skeleton. Our literature search showed that these striking arthroscopic findings have not been made public to date. We report a typical case of mucopolysaccharidosis type IV. We show and, in particular, correlate the arthroscopic with the histologic findings. In particular, the comparison between arthroscopy and light microscopy showed a remarkable extensive delamination of the chondral layer from subchondral bone of both knee joints. These findings should encourage further research, especially of the osteochondral borderline.